Transplant rejection

Definition

Transplant rejection is a process in which a transplant recipient's immune system attacks the transplanted organ or tissue.

Alternative Names

Graft rejection; Tissue/organ rejection

Causes

Your body's immune system usually protects you from substances that may be harmful, such as germs, poisons, and sometimes cancer cells.

These harmful substances have proteins called antigens coating their surfaces. As soon as these antigens enter the body, the immune system recognizes that they are not from that person's body and that they are "foreign," and attacks them.

When a person receives an organ from someone else during transplant surgery, that person's immune system may recognize that it is foreign. This is because the person's immune system detects that the antigens on the cells of the organ are different or not "matched." Mismatched organs, or organs that are not matched closely enough, can trigger a blood transfusion reaction or transplant rejection.

To help prevent this reaction, doctors type, or match both the organ donor and the person who is receiving the organ. The more similar the antigens are between the donor and recipient, the less likely that the organ will be rejected.

Tissue typing ensures that the organ or tissue is as similar as possible to the tissues of the recipient. The match is usually not perfect. No two people, except identical twins, have identical tissue antigens.

Doctors use medicines to suppress the recipient's immune system. The goal is to prevent the immune system from attacking the newly transplanted organ when the organ is not closely matched. If these medicines are not used, the body will almost always launch an immune response and destroy the foreign tissue.

There are some exceptions, though. Cornea transplants are rarely rejected because the cornea has no blood supply. Also, transplants from one identical twin to another are almost never rejected.

There are three types of rejection:

Hyperacute rejection occurs a few minutes after the transplant when the antigens are completely unmatched. The tissue must be removed right away so the recipient does not die. This type of rejection is seen when a recipient is given the wrong type of blood. For example, when a person is given type A blood when he or she is type B.

Acute rejection may occur any time from the first week after the transplant to 3 months afterward. All recipients have some amount of acute rejection.

Chronic rejection can take place over many years. The body's constant immune response against the new organ slowly damages the transplanted tissues or organ.

Treatment

The goal of treatment is to make sure the transplanted organ or tissue works properly, and to suppress your immune system response. Suppressing the immune response may prevent transplant rejection.

Medicines will likely be used to suppress the immune response. Dosage depends on your condition and may be very high while the tissue is being rejected. After you no longer have signs of rejection, the dosage will likely be lowered.

Outlook (Prognosis)

Some organ and tissue transplants are more successful than others. If rejection begins, medicines that suppress the immune system may stop the rejection. Most people need to take these medicines for the rest of their life.

Even though medicines are used to suppress the immune system, organ transplants can still fail because of rejection.

Single episodes of acute rejection are easy to treat and rarely lead to organ failure.

Chronic rejection is the leading cause of organ transplant failure. The organ slowly loses its function and symptoms start to appear. This type of rejection cannot be effectively treated with medicines. Some people may need another transplant.

Possible Complications

Certain cancers (in some people who take strong immune-suppressing drugs for a long time)

Infections (because the person's immune system is suppressed by taking immune-suppressing medications)

Loss of function in the transplanted organ/tissue

Side effects of medicines, which may be severe

When to Contact a Medical Professional

Call your health care provider if the transplanted organ or tissue does not seem to be working properly, or if other symptoms occur. Also, call your health care provider if you have side effects from medicines you are taking.